1. Field of the Invention
The present invention relates generally to containers, specifically to plastic drums of the stackable type.
2. Description of the Prior Art
To achieve structural strength with a miniumum of weight, one form of conventional plastic container or drum includes a cylindrical central portion merging on either side thereof into upper and lower sections which are tapered inwardly relative to the longitudinal axis of the drum. These upper and lower sections terminate in generally planar end walls. The resulting plastic drum therefore has a keg-like shape, in contrast to the generally cylindrical shape of conventional steel drums.
Because of their shape, conventional cylindrical steel drums can be easily rolled, stacked and manipulated in stable geometric arrangements. In contrast, the plastic drums with curved upper and lower portions are difficult to handle and stack.
In U.S. Pat. No. 3,889,839, issued to Butz and Simon and entitled, "Blow Molded Drum", and assigned to asignee of the present application, there is shown a drum configuration having flat, recessed indentations on its upper and lower sidewall surfaces near the shoulder thereof, to facilitate handling of the drum by a fork lift. While this improvement results in easier handling, it does not result in a plastic drum having the same rolling stacking and handling characteristics as a conventional cylindrical steel drum.
The German firm of Mauser is currently manufacturing a plastic drum having a plastic handling ring at each end which extends beyond the outermost diameter of the body of the drum and which extends beyond the planar end walls of the drum. It is understood that these rings are formed by putting a separate piece of plastic in the mold when the drum is formed, and the rings therefore are permanently welded to the plastic of the drum.
This technique not only slows production of the drums, but prevents replacement of the rings when they become damaged. These rings have the further disadvantage in that any spillage that accumulates on the top outer surface of the drum during filling is retained there by the ring.
When the drum is rolled, only the rings make contact with the ground and the center portion of the drum is substantially unsupported. Because the rings extend beyond the ends of the drum, the drums cannot be safely stacked without the use of pallets.
Thus, it is seen that there is a need for a plastic, keg-like drum to which optional handling rings can be removably attached and which, when in place, enable the plastic drum to be handled, rolled and stacked as easily and with the same means as conventional, cylindrical steel drums.